1. Field of the Invention
This invention relates to testing. Specifically, the present invention relates to testing fiber optic cables.
2. Description of the Related Art
Most telecommunication companies employ fiber optic cables for the transmission of various types of data and voice communications. Fiber optic cables provide greater bandwidth as compared to conventional copper lines. Additionally, fiber optic cables have a high degree of immunity from interference and cross talk. Oftentimes, fiber optic cables are buried for safety and aesthetics. Since fiber optic cables are commonly buried, it is difficult to locate the buried portion of the fiber optic cable.
In conventional approaches a cable locating system is employed to facilitate locating buried fiber optic cable. The buried fiber optic cable is usually configured with a metallic component (e.g. sheath) running through the length of the cable. The fiber optic cable is manufactured with steel strength members that run throughout the length of the fiber cable. In addition, the cable has a copper/steel clad sheath around the tube that houses the fibers. An electrical signal is generated and conducted through the metallic sheath of the fiber optic cable. The electric signal, which is conducted along the entire length of the fiber optic cable, produces an electromagnetic field and also produces a voltage on the metallic sheath. Technicians operating locating equipment identify the location of the fiber optic cable by detecting the electromagnetic field. For the cable locating system to function properly, the metallic component of the fiber optic cable must remain isolated from the earth. In addition, the metallic component must be grounded on one end and isolated from ground along the cable's entire length.
Since the sheath is a metallic component, the fiber optic cable is susceptible to lightning strikes and induction caused by power lines. Lightning strikes on or near a fiber optic cable can cause significant damage to the cable, reducing or eliminating the operability of the fiber optic cable. In addition, power lines typically generate power in the range of 60 Hz. The 60 Hz signal generated from the power lines create induction, which interferes with the electromagnetic field. To reduce the problems associated with lightning strikes and power line induction, filter/protector units are positioned along the length of the fiber optic cable.
The filter/protector units are installed along the length of the fiber optic cable to minimize the damage caused by lightning strikes and interference from nearby power lines. The filter/protector units serve the dual purpose of reducing or eliminating the 60 Hz signal interference caused by power lines and provide a quick path to ground when lightning strikes the cable. While existing filter/protector units generally provide effective protection against damage from lightning strikes and interference from power lines, if the filter/protector unit is damaged or malfunctions, the cable locating system may be rendered inoperable.
Several problems may result from damaged or defective filter/protector units. With a failed or faulty filter/protector unit, there is limited protection to the fiber optic cable against lightning strikes and induction from power lines. Additionally, if one filter/protector unit fails or malfunctions, the entire locating system for the associated fiber optic cable may be rendered inoperative. Consequently, the detrimental effects of a damaged or malfunctioning filter/protector unit are significant.
Currently, faulty or malfunctioning filter/protector units are determined by excavating the fiber optic cable or waiting for the symptoms of a malfunctioning filter/protector unit to manifest itself during operation. Using conventional methods, locating malfunctioning filter/protector units is time consuming, costly, and results in higher periods of down time. In addition, locating a malfunctioning filter/protector unit during operations is inconvenient for customers. Currently, there is no existing method or apparatus for efficiently testing filter/protector units to ensure that the units are functioning properly, prior to each filter/protector unit's failure.
Thus, there is a need for a method and apparatus that efficiently and effectively troubleshoots filter/protector units prior to failure. There is a need for a method and apparatus that tests and locates filter/protector units prior to failure. Lastly, there is a need for a method and apparatus that provides automated testing of filter/protector units.